Atmosphere Aerospace Engineering 2011 Project Lead The Way

Atmosphere Aerospace Engineering © 2011 Project Lead The Way, Inc.

Earth’s Atmosphere • Mixture of gases § 78% Nitrogen, 21% Oxygen and other gases § Sustains life § Protects us from solar radiation • Thin sheet of air 60 miles thick § Relative comparison § Basketball wrapped tightly with plastic sheet

Earth’s Atmosphere Layers § § § Troposphere Tropopause Stratosphere Mesosphere Thermosphere

Air Pressure • Air above exerts pressure below § 101. 3 k. Pa (14. 7 psi) means that column (97 km or 60 miles) of air sitting on two thumbnails is 5. 5 kg (14. 7 lb) § Density and pressure higher close to ground

Standard Atmospheric Conditions Aerospace engineers use a standard to compare measurements such as speed § 15 OC and 101. 3 k. Pa (Kilo Pascals) § 59 OF and 14. 7 psi

Earth’s Atmosphere Conditions

Earth’s Atmosphere Conditions Lapse rate in troposphere (11 km)

Earth’s Atmosphere Conditions • Air density changes based on pressure and temperature • Generally air density lowers as it climbs to higher altitudes

Earth’s Atmosphere Conditions • Mount Everest is 8, 848 m (29, 029 ft) tall • Similar altitude of jet aircraft • Climbers acclimatize over long period of time or breathe supplemental oxygen • Pilots must react quickly to receive supplemental oxygen if cabin loses pressure • Causes of pressure loss – Fuselage integrity failure (leak) – Window failure

Aircraft Speed

Aircraft Speed • Air molecules must move as aircraft passes through atmosphere • Air compressed at speeds beyond ~ 400 kph (250 mph) • Air resistance is significant when close to speed of sound • Transition to beyond speed of sound creates shock waves and sonic booms

Aircraft Speed • Mach (M) § Decimal number representing the true airspeed relationship to the local speed of sound: 1, 225 kph or 761 mph at sea level and standard conditions • • Subsonic: < Mach 1 Supersonic: Mach 1 and 5 Hypersonic: Mach 5 and 10 High-Hypersonic: Mach 10 and 25 § Speed of sound changes with temperature § Higher altitudes are cooler, so Mach threshold is lower

References Basic weather theory. In Jeppesen Private pilot: Guided flight discovery (pp. 6 -2 – 6 -7). (2007). Englewood, CO: Jeppesen Sanderson, Inc. (2006). Guided flight discovery commercial pilot images [CD-ROM]. Englewood, CO: Jeppesen Sanderson, Inc. National Aeronautics and Space Administration (2010). Atmosphere. Retrieved from http: //www. grc. nasa. gov/WWW/K 12/airplane/atmosmet. html US Navy. (1999). F/A-18 hornet breaks the sound barrier. Retrieved from http: //www. navy. mil/view_single. asp? id=1445

References Wikipedia. (2011). Mount Everest from Kalapatthar. Retrieved from http: //commons. wikimedia. org/wiki/File: Everest_kalapatt har. jpg